Welcome to the forum Stan, have a look at my links below to see my outdated vid of my line and my build spelt in blue text.
Best advice I can give is to think a little while on what you want and how products may fit to that requirement. UK, US, European, Narrow Gauge, Standard Gauge and also what line. Thinking through some of these options can help you save lots of $ on expensive Locomotives or Coaches that eventually will not fit in with your theme if you have one.
Of course many would say just buy what you like and run it, nothing wrong with that. I did a lot of that before I settled down on a Harz East German Metre gauge theme, once that was decided it focused my mind on products, jumping for joy when something unexpected (Train-line45 Mallets for example) popped up on the market.
Good luck with your journey, not sure what your 30th anniversary set will have in it, but if a Stainz it and possibly the stock can always be modified to maybe fit in with a future theme if you have the ability.